To test the hypothesis: PTHrP is associated with the development of lung surfactant. The development of lung surfactant determines the severity of RDS at birth. To test this hypothesis we will measure PTHrP, surfactant phospholipids, and surfactant proteins A and B in tracheal aspirates and gastric aspirates of patients intubated for RDS. We will subsequently evaluate the relationship between PTHrP concentration, surfactant level, and respiratory status in the immediate post-natal period to establish whether PTHrP levels correlate with lung maturity and function at birth.